Consider what happens when a sample of the explosive TNT...

Consider what happens when a sample of the explosive TNT (Section 8.8: "Chemistry Put to Work: Explosives and Alfred Nobel") is detonated under atmospheric pressure. (a) Is the detonation a spontaneous process? (b) What is the sign of $q$ for this process? (c) Can you determine whether $w$ is positive, negative, or zero for the process? Explain. (d) Can you determine the sign of $\Delta E$ for the process? Explain.

Consider what happens when a sample of the explosive TNT (Section 8.8: "Chemistry Put to Work: Explosives and Alfred Nobel") is detonated under atmospheric pressure.
(a) Is the detonation a spontaneous process? (b) What is the sign of $q$ for this process? (c) Can you determine whether $w$ is positive, negative, or zero for the process? Explain. (d) Can you determine the sign of $\Delta E$ for the process? Explain.

Key Concepts

Spontaneous Process

A spontaneous process in thermodynamics is one that, once initiated, proceeds on its own without needing continuous external influence. In chemical reactions, spontaneity is often tied to the overall energy changes, with exothermic reactions, such as detonations, typically being spontaneous once the activation energy barrier is overcome.

Exothermic Reactions and Heat Transfer (q)

Exothermic reactions release heat to their surroundings. In thermodynamic sign conventions, when a reaction liberates heat, the heat transfer (q) is considered negative because energy flows out of the system. This is characteristic of explosive processes where a large amount of energy is released rapidly.

Work in Thermodynamic Processes (w)

Work in a thermodynamic context, particularly expansion work, is defined as the energy transferred by the system doing work on its surroundings, calculated as -P?V. When a reaction produces gases that expand against atmospheric pressure, the work done by the system is negative under the sign convention, indicating that energy is spent in doing work on the surroundings.

Internal Energy Change (?E) and the First Law of Thermodynamics

The first law of thermodynamics relates the change in internal energy (?E) to the sum of heat (q) and work (w) exchanged with the surroundings, expressed as ?E = q + w. In exothermic reactions where both heat is released (q is negative) and work is done by the system (w is negative), the overall internal energy change (?E) is also negative, indicating a net loss of energy from the system.

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